All designations "-G" means in principle "not specified". Only tensile strength is specified.
For WB36 often the 0,5%Mo TIG rods can be taken for root and fil with 1%Ni-and 0,3-0,5%Mo. Also depending on required charpy values (at -40°C?). PHOENIX SH Schwarz 3 K Ni (SMAW). UNION S3NiMo1 with UV 420TT(R) or UV421TT (SAW). Böhler DMO-IG (GTAW).